Jack_dotson wrote: "I always use one for HT, but not for music unless listening for 5.1 SACD, which I normally listen to in two channel as well."
Well, of course. Why use a center speaker if there is no center channel signal?
OTOH, creating a phantom center when there is a discrete center signal creates inevitable phase/time errors in the process. This is noticeable even on-axis but mostly with music sources.
Kal